Reaction valve drilling jar system

ABSTRACT

An apparatus and method for drilling is disclosed, including a drill string with at least one jar and one reaction valve. Drilling fluid flows through the reaction valve. The reaction valve is selectively throttled, which creates a differential pressure across the valve seat. The differential pressure creates an axial force that is transferred to the jar, which aids in cocking or firing the jar. In an embodiment, a reaction valve throttles downward fluid flow to create a downward compressional force on the jar, while in another embodiment, a reaction valve throttles upward fluid flow to create an upward tensile force on the jar. Upward and downward fluid flow may be alternatively throttled for alternately firing the jar upwards and downwards. A bypass valve may be included in the drill string for establishing a drilling fluid flow path when such may be otherwise obstructed by foreign matter in the wellbore.

TECHNICAL FIELD

The present disclosure relates generally to oilfield equipment, and inparticular to downhole tools, drilling systems, and drilling techniquesfor drilling wellbores in the earth. More particularly still, thepresent disclosure relates to an improvement in systems and methods forfreeing stuck drill pipe.

BACKGROUND

During the drilling of an oil or gas wellbore or the like, situationsare encountered wherein a component of the drill string becomes lodgedin the wellbore. When the static force necessary to move a drill stringexceeds the rig's capabilities or the tensile strength of the drillpipe, the drill string is stuck and can no longer be moved or rotated. Ajar is a tool that is prepositioned within the drill string to free anyportion of the drill sting which may become stuck.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described in detail hereinafter with reference to theaccompanying figures, in which:

FIG. 1 is an elevation view in partial cross section of a drillingsystem that employs a drill string with drill pipe, a jar, anaccelerator, and a reaction valve disposed between the drill pipe andthe jar according to an embodiment;

FIG. 2 is a simplified axial cross section of a jar of FIG. 1;

FIG. 3A is a simplified axial cross section of an accelerator of FIG. 1,shown in an unloaded state with no force applied;

FIG. 3B is a simplified axial cross section of the accelerator of FIG.3A, shown in a loaded state with force applied;

FIG. 4 is a simplified axial cross section of a reaction valve accordingto an embodiment, showing a rotor and stator that collectively define anadjustable valve seat for producing an axial reactive force in responseto throttling of fluid flow therethrough;

FIG. 5A is a simplified transverse cross section taken along line 5A-5Aof FIG. 4, showing details of the rotor of the reaction valve of FIG. 4;

FIG. 5B is a simplified transverse cross section taken along line 5B-5Bof FIG. 4, showing details of the stator of the reaction valve of FIG.4;

FIG. 6 is an elevation view in partial cross section of a drillingsystem that employs a pipe-in-pipe drill string, a jar, an accelerator,and a reaction valve disposed between the drill pipe and the jaraccording to an embodiment, with details of the pipe-in-pipe drillstring shown in a blown up section for clarity;

FIG. 7A is a simplified axial cross section of a flow diverter of FIG.6, showing ports for cross-connecting a wellbore annulus with an innerpipe;

FIG. 7B is a simplified transverse cross section of the flow diverter ofFIG. 7A, taken along line 7B-7B of FIG. 7A, showing ports forcross-connecting a wellbore annulus with an inner pipe;

FIG. 8A is a simplified axial cross section of a dual upflow/downflowreaction valve according to an embodiment for use with the pipe-in-pipedrilling system of FIG. 6, showing an inner rotor and stator assemblyfor throttling up-flow and an annular rotor and stator assembly forthrottling downflow;

FIG. 8B is a simplified transverse cross section of the dual reactionvalve of FIG. 8A taken along line 8B-8B of FIG. 8A; and

FIG. 9 is a flow chart of a method for drilling a wellbore according toan embodiment, demonstrating use of the drilling system of FIGS. 1-8Bfor increasing effectiveness of jarring operations.

DETAILED DESCRIPTION

The foregoing disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed. Further, spatiallyrelative terms, such as “beneath,” “below,” “lower,” “above,” “upper,”“uphole,” “downhole,” “upstream,” “downstream,” and the like, may beused herein for ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. The spatially relative terms are intended to encompassdifferent orientations of the apparatus in use or operation in additionto the orientation depicted in the figures.

FIG. 1 is an elevation view in partial cross-section of a drillingsystem 20 including a bottom hole assembly 90 according to anembodiment. Drilling system 20 may include a drilling rig 22, such asthe land drilling rig shown in FIG. 1. However, teachings of the presentdisclosure may be used in association with drilling rigs 22 deployed onoffshore platforms, semi-submersibles, drill ships, or any otherdrilling system for forming a wellbore.

Drilling rig 22 may be located proximate to or spaced apart from wellhead 24. Drilling rig 22 may include rotary table 38, rotary drive motor40 and other equipment associated with rotation of drill string 32within wellbore 60. Annulus 66 is formed between the exterior of drillstring 32 and the inside diameter of wellbore 60. For some applicationsdrilling rig 22 may also include top drive motor or top drive unit 42.Blowout preventers (not expressly shown) and other equipment associatedwith drilling a wellbore may also be provided at well head 24.

The lower end of drill string 32 includes bottom hole assembly 90, whichcarries at a distal end a rotary drill bit 80. Drilling fluid 46 may bepumped from reservoir 30 by one or more mud pumps 48, through conduit34, to the upper end of drill string 32 extending out of well head 24.The drilling fluid 46 then flows through the longitudinal interior 33 ofdrill string 32, through bottom hole assembly 90, and exits from nozzlesformed in rotary drill bit 80. At bottom end 62 of wellbore 60, drillingfluid 46 may mix with formation cuttings and other downhole fluids anddebris. The drilling fluid mixture then flows upwardly through annulus66 to return formation cuttings and other downhole debris to thesurface. Conduit 36 may return the fluid to reservoir 30, but varioustypes of screens, filters and/or centrifuges (not expressly shown) maybe provided to remove formation cuttings and other downhole debris priorto returning drilling fluid to reservoir 30. Various types of pipes,tube and/or hoses may be used to form conduits 34 and 36.

According to an embodiment, bottom hole assembly 90 includes a downholemud motor 82, which may have a bent housing. Bottom hole assembly 90 mayalso include various other tools 91, such as those that provide loggingor measurement data and other information from the bottom of wellbore60. Measurement data and other information may be communicated from end62 of wellbore 60 using measurement while drilling techniques andconverted to electrical signals at the well surface to, among otherthings, monitor the performance of drilling string 32, bottom holeassembly 90, and associated rotary drill bit 80.

Drill string 32 includes a jar 100 for freeing stuck pipe. Jar 100 maybe located in bottom hole assembly 90 or elsewhere along drill string32. In some configurations, multiple jars 100 may be included in drillstring 32. In the case of multiple jars 100, it is preferable that thejars 100 not be located in close proximity to one another as suchconfiguration can impose excessive loads during jarring operations. Adistance of 1500 feet is preferably maintained between multiple jars100. One or more drill collars 108 may also be included in drill string32, and in some configurations, drill collars 108 are positioned abovejar 100. However, one or more sections of heavy weight drill pipe may besubstituted for drill collars 108. Two predominant reasons why drillingpipe become stuck include mechanical sticking and differential stickingMechanical sticking is caused by a physical obstruction or restrictionbetween a portion of the drill string and the wellbore wall, such aswhen an unconsolidated formation, earthen cuttings or other debriscollect in the annulus between the drill string and the wellbore or whenthe shape or size of the wellbore and that of the drill string areincompatible. Other causes of interference may include an under-gaugehole, a stiff drill string, unstable formations, ledges, doglegs, andbuckled casing. Differential sticking is caused when hydrostaticpressure in the drilling fluid column is greater than the pore pressurein the permeable formation, which forces the drill string into tightengagement with the wellbore wall.

Jar 100 is pre-positioned in drill string 32 to loosen any portion ofdrill string 32 which may become stuck. Jar 100 operates on theprinciple of stored potential energy. The potential energy available tojar 100 comes from over-pull (tensile) or set-down (compressive) forcesapplied to the drill pipe at the surface. Jarring is the process ofdynamically transferring strain or compression energy stored in thedrill string to the jar, which converts that energy into kinetic energythat is concentrated at the point where the pipe is stuck.

Jar 100 may include a mandrel, which slides within a sleeve, and adetent mechanism. The mandrel functions as a hammer, and the sleevefunctions as an anvil. The detent mechanism, restricts the movement ofthe mandrel before freely releasing it (i.e., “firing”), so thatsufficient potential energy accumulates within the drill string and istransferred to the mandrel to cause, upon firing, the mandrel to rapidlymove and strike the sleeve.

Jar 100 may be a double acting jar that can provide jarring force bothupwards and downwards. The separate functions of jarring upward ordownward may be accomplished in any sequence; that is, up only, downonly, or alternately up and down. Jar 100 may be run in drill string 32either in tension, in which the mandrel is completely extended, or incompression, in which the mandrel is completely retracted. In eitherposition, mandrel movement is prevented until jarring becomes necessary.If run under tension, the operator must first apply compression to drillstring 32 in order to cock the mandrel into a position that allowsupward firing. Conversely, if run under compression, the operator mustfirst apply tension to drill string 32 in order to cock the mandrel fordownward firing.

In operation, to fire jar 100 upwards, the operator applies over-pulltension at the top of drill string 32 while the lower end of drillstring 32, which is stuck, remains stationary. The force of the upwardpull is directly applied to the mandrel. However, because the detent injar 100 restricts the upward movement of the mandrel during this loadingphase, the drill pipe is physically stretched and stores strain energy.

After a predetermined time has elapsed or a predetermined force isreached, jar 100 fires:

The detent mechanism trips, allowing the mandrel to freely and rapidlyaccelerate upwards under the tensile force applied to it by thestretched drill string 32. The drill pipe is thus set into motion, andbecause of the high mass of the drill collars 108 or heavy weight drillpipe included in drill string 32 just above jar 100, momentum is rapidlygained. At the end of its upward travel, the mandrel strikes the sleeve.This impact creates an impulse, and the kinetic energy of the movingdrill string is transmitted as shock wave that travels up and down thedrill string to free the stuck portion of the drill string. Afterfiring, drill string 32 must be lowered until the drill string weightimposes a sufficient compressive force on jar 100 to reset the mandrelfor another upward jarring cycle. Alternatively, jar 100 may beimmediately fired in a downward direction.

To fire jar 100 downwards, instead of over-pull applied to the drillpipe, the weight of drill string 32 is at least partially released byrig 22, delivering a compressive set-down force to the mandrel. Thedetent in jar 100 restricts the downward movement of the mandrel duringthis loading phase. After a predetermined time has elapsed or apredetermined force is reached, jar 100 fires: The detent mechanismtrips, allowing the mandrel to freely and rapidly accelerate downwardsunder the weight of the drill string. The drill pipe is thus set intomotion, and because of the high mass of the drill collars 108 or heavyweight drill pipe typically included in the drill string just above jar100, momentum is rapidly gained. At the end of its downward travel, themandrel strikes the sleeve. This impact creates an impulse, and thekinetic energy of the moving drill string 32 is transmitted as a shockwave that travels along drill string 32 to free the stuck portion. Afterfiring, drill string 32 must be raised until a sufficient tension resetsthe mandrel for another downward jarring cycle, or jar 100 may beimmediately fired in an upward direction.

Jar 100 may generally be either of two types based on the detentmechanism: Mechanical and hydraulic. A mechanical jars is actuated usinga series of springs, locks and rollers with release mechanisms. Amechanical jar fires upward at a preset tensile force and downward at apreset compressional force, which normally exceed the forces reachedduring drilling. Firing is independent of the time of the loading phase.A hydraulic jar, on the other hand, operates by moving a piston pullingthrough a fluid-filled hydraulic cylinder. Fluid passes from one side ofthe piston to the other through an orifice, triggering valve, or similarrestriction which initially limits flow to create a time delay duringthe loading phase and then freely opens the flow path to trip the detentmechanism and fire the jar. In some hydraulic jars, the pressure pistonmust move a predetermined distance in order to bypass the restriction oropen the triggering valve. The built-in delay is designed to allow theoperator sufficient time to apply the desired tensile or compressiveforce to the drill string before the flow restriction is cleared or thetriggering valve is opened. Therefore, varying the metering rate of thefluid through the restriction affects the magnitude of impact.

A reaction valve 112 is included in drill string 32 and may be locatedin bottom hole assembly 90 or elsewhere in drill string 32. In someconfigurations, reaction valve 112 is positioned above jar 100.Furthermore, multiple reaction valves 112 may be included in drillstring 32, particularly when multiple jars 100 are included in drillstring 32. Reaction valve 112 is described in greater detail below.

A bypass valve 118 may be included in drill string 32 and may be locatedin bottom hole assembly 90 or elsewhere in drill string 32. Bypass valve118 may be collocated with reaction valve 112, and indeed it may behoused in a common sub with reaction valve 112. Additionally, multiplebypass valves 118 may be included in drill string 32, particularly inarrangements in which multiple reaction valves 112 are included in drillstring 32. Bypass valve 118 is described in greater detail below.

An accelerator 122 may optionally be included in bottom hole assembly 90or elsewhere in drill string 32. Accelerator 122 may be positioned abovejar 100. Moreover, multiple accelerators 122 may be included in drillstring 32, particularly in arrangements in which multiple jars 100 areincluded in drill string 32. Accelerator 122 is described in greaterdetail below.

FIG. 2 is an axial cross section of the operable portion of adouble-acting hydraulic jar 100 according to an embodiment, which issimplified for ease of illustrating the jar's operation. Referring toFIG. 2, jar 100 is arranged for connection within drill string 32 (FIG.1). Although not illustrated, jar 100 may include a flow path fordrilling fluid to pass through the tool. Jar 100 may include a mandrel200 that slides within a sleeve 202. Sleeve 202 is filled with a fluid.Mandrel 200 functions both as a piston and as a double-headed hammer.The upper end 206 of sleeve 202 functions as an anvil for upwardjarring, and the lower end 208 of sleeve 202 functions as an anvil fordownward jarring. Mandrel 200 is connected by a connecting rod 203 tothe upper end 211 of jar 100, and sleeve 202 is connected to the lowerend 213 of jar 100.

A detent mechanism 204, which in the embodiment illustrated in FIG. 2includes an inward projection shoulder that provides a fluid restrictionin sleeve 202, operates to delay motion of mandrel 200 within sleeve 202to provide a loading phase for buildup of over-pull tension or set-downcompression within the drill string. Detent mechanism 204 creates afluid restriction across mandrel 200 that slows the initial stroke ofthe mandrel 200. Near the end of both the upstroke and the downstroke,detent 204 no longer creates a fluid restriction; the piston moves fromthe restrictive area into a larger area, allowing the compressed fluidto flow freely around mandrel 200. The pressure across mandrel 200equalizes, and mandrel 200 may freely accelerate under the potentialenergy accumulated within the drill string during the loading phase,rapidly strike upper sleeve end 206 or lower sleeve end 208, much as ahammer would strike an anvil. This striking action is commonly referredby routineers as firing the jar.

The time required for jar 100 to fire and the intensity with which jar100 fires is a function of the magnitude of the applied tension orcompression. Over-pull tension or set-down compression influences theflow rate of the fluid within sleeve 202 past mandrel 200 through therestriction created by detent 204. Although low applied force can firethe jar, greater over-pull tension or set-down compression producesquicker and more intense jar firing.

Mandrel 200 and sleeve 202 may have a spline or polygonal transversecross sectional profile 220 that allows mandrel 200 to transfer drillstring torque through jar 100 with minimal backlash and withoutaffecting the magnitude or the time delay of the jarring operation.

Referring to FIGS. 1 and 2, two jarring parameters determine the abilityto free stuck pipe: Impact force and impulse. Impact force is defined asthe peak force caused by the striking of mandrel 200 against sleeve 202,while impulse is a measurement of the change of momentum due to thejarring. Both impact force and impulse are influenced primarily by thenumber of drill collars 108 above jar 100. Fewer drill collars 108result in a higher impact force, and more drill collars 108 deliver agreater impulse. The impact force produced by jar 100 is limited by theover-pull tension or slack-off weight available. Over-pull tension mayapproach the yield strength of drill string 32, but the availableslack-off weight may be much less than the total drill string weight dueto buckling limitations. Maximum effect may be achieved by optimizingboth the placement of jar 100 and the number of drill collars 108 withindrill string 32.

Additionally, differential pressure between the interior 33 of drillstring 32 and annulus 60 acts on the sealed cross-sectional area ofmandrel 200, which may create a pump-open force that urges mandrel 200to extend. During normal drilling, pump-open force has no effect onweight on bit. However, when jarring upward, pump-open force must beadded to the over-pull tension to obtain actual tension at jar 100, andwhen jarring downward, pump-open force must be subtracted from theslack-off weight to obtain actual compression at jar 100. Accordingly,pump-open force may be harnessed to aid in upward jarring by increasingthe mud pump rate, which increases pump-open force.

It may be the case that drill string 32 is too short to allow foreffective jarring. That is, drill string 32 may be too short to allowadequate stretching during over-pull, or it may be too light to provideadequate set-down weight, particularly if heavy weight drill pipe isused in place of drill collars 108. Accelerator 122 may be included indrill string 32 to significantly amplify jar impact and impulse. Usingaccelerator 122 can effectively double the impact force of jar 100.Moreover, accelerator 122 may relieve stress due to jarring operationsfrom surface equipment. Accelerator 122 may be used in all types ofwellbores, although accelerator 122 may be particularly beneficial inhigh-angle and horizontal wellbores, plastic salt sections, and otherareas with high probability of differential sticking.

FIGS. 3A and 3B are axial cross sections of an accelerator 122 accordingto an embodiment. Accelerator 122 includes an inner mandrel 300 that isslidingly received within an outer barrel 302 Inner mandrel 300 includesa piston 304 that slides within a cylinder 306. Cylinder 306 is filledwith a fluid 308, which may be a silicon fluid, for example. However, aspring may be used in place of fluid 308. In FIG. 3A, no load is appliedto accelerator 122. When a tensile load is applied to accelerator 122,as shown in FIG. 3B, mandrel 300 and piston 304 are displaced withinbarrel 302 and cylinder 306, respectively, which compresses fluid 308and stores potential energy.

When jar 100 fires, the stored potential energy in accelerator 122 isalso released. The potential energy stored in and released fromaccelerator 122 accelerates the working mass of drill string 32 abovejar 100 much more efficiently than does energy stored in a stretcheddrill string, because accelerator 122 eliminates the wellbore frictionand drag generated over hundreds of meters of drill pipe.

Referring back to FIG. 1, reaction valve 112 is positioned above jar 110and functions to increase a downward jar. Reaction valve 112 ispositioned within the downward flow path of drilling fluid 46 throughdrill string 32. Reaction valve may be selectively throttled whiledrilling fluid is being circulated down through drill string 32 and upthrough annulus 66 of wellbore 60 by mud pumps 48. Throttling reactionvalve 112 creates, in an isenthalpic process, a pressure drop across theseat of reaction valve 112. The differential pressure acts against theseat so that reaction valve 112 applies a downward throttling force thatbears down on top of jar 100. The downward throttling force isproportional to the transverse cross sectional area of the seat, uponwhich the differential pressure acts. The downward throttling force isadded to the set-down weight, and it may be employed to increase theintensity of downward jarring or to reset jar 100 for upward jarring.The downward throttling force can be varied by both varying the degreeof throttling of reaction valve 112 and by increasing the output of mudpumps 48.

FIG. 4 is an axial cross section of a reaction valve 112 according to anembodiment. FIGS. 5A and 5B are transverse cross sections of the rotorand stator, respectively, of reaction valve 112, which together form theseat of reaction valve 112. Referring to FIGS. 4-5B, reaction valve 112includes a tubular body 400 which defines an axial flow path 402. Theupper and lower ends of body 400 may include connectors for assemblingreaction valve within drill string 32 or bottom hole assembly 90 (FIG.1).

A valve seat is formed by a rotor 404 and a stator 406. Rotor 404 ischaracterized by having the shape of a ring with arcuate vanes 410formed therein that define arcuate flow passages 412 therethrough.Stator 406 is substantially similar to rotor 404, having arcuate vanes414 and flow passages 416. Stator 406 is fixed within body 402. Rotor404 is rotatively received within body 402 and adjacent to stator 406. Adrive mechanism 420 is operable to throttle reaction valve 112, i.e., toselectively rotatively position rotor 404 between a fully open position,in which flow passages 412 and 416 are aligned, and a shut position, inwhich vanes 410 substantially cover flow passages 16 so as to blockfluid flow.

Due to throttling across rotor 404 and stator 406, the pressure P₁upstream of rotor 404 is greater than the pressure P₂ downstream ofstator 406. The seat area A_(S) is the combined area of rotor vanes 410and stator vanes 414 exposed to the flow stream, which is varied asrotor 404 is rotatively positioned. The throttling force F_(T) is givenas:

F _(T) =A _(S)(P ₁ −P ₂)  (Equation 1).

Drive mechanism 420 may be a solenoid winding, servo motor, or similarpositioning device, and it may include a bearing assembly. A controlsystem 424 controls drive mechanism 420. If desired, reaction valve 112may be controlled from the surface via conventional telemetry. Reactionvalve 112 may be programmed so that when it receives a throttle command,it throttles for a predetermined period and then opens againautomatically. Reaction valve 112 may include one or more sensors 426,such as a transducer, an accelerometer, or an axial strain gauge, formeasuring tension and compression. Sensor 426 allows reaction valve 112to autonomously detect when upward and downward jarring has occurred.Reaction valve 112 may also be arranged to alternatively throttle shutand open automatically based on input from sensor 426 for repeatedjarring and/or resetting. Although not illustrated, valve 112 mayinclude a pressure-actuated bypass, which will actuate in the eventvalve 112 fails in the shut condition. In configurations in whichmultiple reaction valves 112 are included in drill string 32 (FIG. 1),each reaction valve 112 may be independently controlled from the surfacevia conventional telemetry.

Referring back to FIG. 1, it may occur in a mechanically stuck pipesituation that conventional drilling fluid circulation may be lost dueto blockage of annulus 66. Without drilling fluid circulation,throttling reaction valve 112 would have little effect. Accordingly,bypass valve 118 may be positioned just below reaction valve 112 andused to bypass fluid flow from within drill string 32 to annulus 66,thereby allowing flow through reaction valve 112. Bypass valve 118 maybe independently controlled from the surface via conventional telemetry,or it may be controlled by control system 424 of reaction valve 112, forexample.

FIG. 6 is an elevation view in partial cross-section of a drillingsystem 20′ that includes a bottom hole assembly 90′ according to anembodiment in which a Reelwell drilling method pipe-in-pipe drill string32′ is used in place of the conventional drill string 32 of FIG. 1.Drill string 32′ includes an inner pipe 110 that is coaxially disposedwithin an outer pipe 120. Inner pipe 110 and outer pipe 120 may beeccentric or concentric. An annular flow path 53 is defined betweeninner pipe 110 and outer pipe 120, and an inner flow path 54 is definedwithin the interior of inner pipe 110. Moreover, annulus 66 is definedbetween the exterior of drill string 32′ and the inside wall of wellbore60. A flow diverter 210 located near the distal end of drill string 32′fluidly connects annulus 66 with inner flow path 54.

As with drilling system 20 of FIG. 1, drilling system 20′ of FIG. 6 mayinclude drilling rig 22 located on land, an offshore platform,semi-submersible, drill ship or the like. Drilling rig 22 may be locatedproximate well head 24 and may include rotary table 38, rotary drivemotor 40 and other equipment associated with rotation of drill string32′ within wellbore 60. For some applications drilling rig 22 mayinclude top drive motor or top drive unit 42. Blow out preventers (notexpressly shown) and other equipment associated with drilling a wellboremay also be provided at well head 24.

The lower end of drill string 32′ includes bottom hole assembly 90,which at a distal end carries a rotary drill bit 80. Drilling fluid 46may be pumped from reservoir 30 by one or more drilling fluid pumps 48,through conduit 34, to the upper end of drill string 32′ extending outof well head 24. The drilling fluid 46 then flows through the annularflow path 53 between inner pipe 110 and outer pipe 120, through bottomhole assembly 90′, and exits from nozzles formed in rotary drill bit 80.At bottom end 62 of wellbore 60, drilling fluid 46 may mix withformation cuttings and other downhole fluids and debris. The drillingfluid mixture then flows upwardly through annulus 66, through flowdiverter 210, and upwards through the inner flow path 54 provided byinner pipe 110 to return formation cuttings and other downhole debris tothe surface. Conduit 36 may return the fluid to reservoir 30, butvarious types of screens, filters and/or centrifuges (not expresslyshown) may be provided to remove formation cuttings and other downholedebris prior to returning drilling fluid to reservoir 30. Various typesof pipes, tube and/or hoses may be used to form conduits 34 and 36.

FIGS. 7A and 7B are axial and transverse cross sections, respectively,of flow diverter 210. Referring to FIGS. 7A and 7B, flow diverter 210 isdisposed between inner pipe 110 and outer pipe 120. Seals 320 may belocated on the top and bottom of flow diverter 210 to prevent annularflow between inner pipe 110 and outer pipe 120 from leaking into thecenter of inner pipe 110. Flow diverter 210 may be keyed to inner pipe110 and outer pipe 120 so as to maintain proper rotational alignment.During operation, drilling fluid 46 (FIG. 36) flows down annular flowpath 53 between inner pipe 110 and outer pipe 120 and throughkidney-shaped passages 211 within flow diverter 210. Concurrently,drilling fluid and earthen cuttings from annulus 66 formed betweenwellbore 60 and outer pipe 120 enters inner pipe 110 via crossover ports212. Inner pipe 110 is capped or plugged at or just below flow diverter210 so that fluid from annulus 66 can only flow upwards within innerpipe 110.

FIGS. 8A and 8B are axial and transverse cross sections, respectively,of a dual reaction valve assembly 412 according to an embodiment, whichmay be suitable for use with the pipe-pip-pipe drilling system 20′ ofFIG. 6. Referring to FIGS. 6, 8A, and 8B, reaction valve 412 includes aninner tubular member 510 coaxially disposed within an outer tubularmember 520 Inner tubular member 510 and outer tubular member 520 arearranged for coupling to inner pipe 110 and outer pipe 120,respectively, of drill string 32′, so that the interior 554 of innertubular member 510 is in fluid communication with inner flow path 54 andthe annular region 553 outside of inner tubular member 510 and inside ofouter tubular member 520 is in fluid communication with annular flowpath 53. Dual reaction valve assembly 412 is located above flow diverter210 so that drilling fluid flow downward in annular region 553, anddrilling fluid, earthen cuttings and reservoir fluid flow upward throughinterior 554 of inner tubular member 510.

Dual reaction valve assembly 412 includes an upflow reaction valve 480located within interior 554 and a downflow reaction valve 482 locatedwithin annular region 553. The upflow and downflow reaction valves 480,482 may be operable independently of one another.

The upflow reaction valve 480 has valve seat formed by a rotor 502 and astator 506. Rotor 502 is characterized by having the shape of a ringwith arcuate vanes formed therein that define arcuate flow passagestherethrough. Stator 506 is substantially similar to rotor 404, havingarcuate vanes 503 and flow passages 516. Stator 506 is fixed withininner tubular member 510. Rotor 504 is rotatively received within innertubular member 510 and adjacent to stator 506. A drive mechanism 530 isoperable to selectively rotatively position rotor 502 between a fullyopen position, in which the flow passages are aligned, and a shutposition, in which the rotor vanes substantially cover flow passages 516so as to block upward fluid flow.

Similarly, the downflow reaction valve 482 has valve seat formed by arotor 503 and a stator 507. Rotor 503 is characterized by having theshape of an annular ring with arcuate vanes 505 formed therein thatdefine arcuate flow passages 509 therethrough. Stator 507 issubstantially similar to rotor 503, having arcuate vanes and flowpassages. Stator 507 is fixed between inner tubular member 510 and outertubular member 520. Rotor 503 is rotatively received between innertubular member 510 and outer tubular member 52 adjacent to stator 507 Adrive mechanism 534 is operable to selectively rotatively position rotor503 between a fully open position, in which the flow passages arealigned, and a shut position, in which rotor vanes 505 substantiallycover the stator flow passages so as to block downward fluid flow.

Drive mechanisms 530 and 534 may include solenoid windings, servomotors, or similar positioning devices. A control system 540 controlsdrive mechanism 530 and 534. In one arrangement, dual reaction valveassembly 412 may be controlled from the surface via conventionaltelemetry. Dual reaction valve assembly 412 may be programmed so thatwhen it receives a throttle command, it throttles for a predeterminedperiod and then opens again automatically. However, dual reaction valveassembly 412 may also include one or more sensors 542, such as atransducer, an accelerometer, or an axial strain gauge, for measuringtension and compression. Such sensor 542 may allow dual reaction valveassembly 412 to autonomously detect when upward and downward jarring hasoccurred. Dual reaction valve assembly 412 may therefore also bearranged to alternatively throttle and open upflow and downflow reactionvalves 480, 482 automatically based on input from sensor 542 forrepeated jarring and/or resetting. In configurations in which multipledual reaction valve assemblies 412 are included in drill string 32, eachdual reaction valve assembly 412 may be independently controlled fromthe surface via conventional telemetry.

It may occur in a mechanically stuck pipe situation that conventionaldrilling fluid circulation may be lost due to blockage of annulus 66.Without drilling fluid circulation, throttling upflow and/or downflowreaction valves 480, 482 would have little effect. Accordingly, a bypassvalve 413 may be positioned just below the lowest dual reaction valveassembly 412 in drill string 32′. Bypass valve 413 may be used to bypassfluid flow from annular flow path 53 to inner flow path 54, therebyallowing upflow and downflow through all dual reaction valve assemblies412. Bypass valve 413 may be independently controlled from the surfacevia conventional telemetry, or bypass valve 413 may be controlled bycontrol system 540 of dual reaction valve assembly 412, for example.

While circulating drilling fluid, downflow reaction valve 482 may beopened and upflow reaction valve 480 throttled to create a pressuredifferential across upflow reaction valve 480 that creates an upwardtension force at dual reaction valve assembly 412. Such upward tensionforce may be used in lieu of or in addition to a surface-appliedover-pull to cock or upward fire jar 100. Similarly, upflow reactionvalve 480 may be opened and downflow reaction valve 482 throttled tocreate a pressure differential across downflow reaction valve 482 thatcreates a downward compression force at dual reaction valve assembly412. Such downward compression force may be used in lieu of or inaddition to a surface-applied slack-off to cock or downward fire jar100. Such apparatus therefore provides enhanced jarring effect andquicker and more effective re-latching of jar 100.

Although drilling systems 20, 20′ have been described herein as using adrilling fluid 46 such as a liquid drilling mud, the systems may also beused with air or gas. Because of the ability of gases to expand, such asystem may provide a greater jarring enhancement.

FIG. 9 is a flow chart of a method for enhancing jarring effectivenessaccording to an embodiment, using exemplar drilling system 20′ of FIG.6, which includes drill string 32′ that has pipe-in-pipe drill pipe, jar100, and dual reaction valve assembly 412 disposed between the drillpipe and jar 100. Jar includes mandrel 200 that is slidingly receivedwithin sleeve 202, as described above with respect to FIG. 2. Referringto FIGS. 2, 6 and 9, if necessary to establish drilling fluid flow at asufficient flow rate, at step 600 bypass valve 413 is opened to connectannular flow path 53 with inner flow path 54. At step 602, drillingfluid pumps 48 are energized to circulate drilling fluid 46 throughdrill string 32′.

Next, as shown in any of steps 610, 620, 630, and 640, drilling fluid isselectively throttled by a reaction valve so as to create a differentialpressure across the reaction valve. The differential pressure creates anaxial force that is transferred to jar 100, which urges mandrel 200 tomove with respect to sleeve 202. For example, by throttling downflowreaction valve 482, mandrel 200 may be urged downward to cock jar 100for subsequent upward firing as shown in step 610 or to fire jar 100downward if jar 100 is run in tension as shown in step 630.Alternatively, upflow reaction valve 480 may be throttled to urgemandrel 200 upward to cock jar 100 for subsequent downward firing asshown in step 640 or to fire jar 100 upward if jar 100 is run incompression as shown in step 620.

For upward jarring, after cocking jar 100 in step 610, in step 615,downflow reaction valve 482 is opened, and upflow reaction valve 480 isthrottled for firing jar 100 upwards. If necessary or desire, surfaceover-pull tension is applied. This process of throttling downflowreaction valve 482 for cocking jar 100 and then throttling upflowreaction valve 480 for firing jar 100 may then be repeated as often asnecessary.

Likewise for downward jarring, after cocking jar 100 in step 640, instep 645, upflow reaction valve 480 is opened, and downflow reactionvalve 482 is throttled for firing jar 100 downwards. If necessary ordesire, the drill string tension is slacked at the surface to applyadditional compressional force on jar 100. This process of throttlingupflow reaction valve 480 for cocking jar 100 and then throttlingdownflow reaction valve 482 for firing jar 100 may then be repeated asoften as necessary.

Drilling system 20′ may also be used to alternatively fire jar 100upwards and downwards. If jar 100 is initially run in hole undercompression, then jar 100 is initially cocked for upward firing.Accordingly, in step 620, downflow reaction valve 482 is opened andupflow reaction valve 480 is throttled to apply a tension force on jar100. As necessary, an over-pull tension may be applied at the surface.Once jar 100 fires in an upward direction, in step 625 upflow reactionvalve 480 is opened and downflow reaction valve 482 is throttled toapply a compression force on jar 100. As necessary, an drill stringtension may be slacked at the surface to apply additional compressionalload on jar 100. After downward firing, the process is repeated. If jar100 is initially run in hole under tension, process for alternatedownward and upward firing is essentially the same as shown in steps 630and 635, except that jar 100 is first fired in the downward direction.

In summary, a drilling system, an assembly for connection to a drillpipe, and a method of drilling a wellbore have been described.Embodiments of the drilling system may generally have: A drill stringdisposed in a wellbore forming a conduit for a flow of drilling fluid,the drill string including a drill pipe, ajar coupled to the drill pipeand having a mandrel that is slidingly received within a sleeve, and areaction valve coupled between the drill pipe and the jar, the reactionvalve being operable to throttle the flow of drilling fluid; anarrangement disposed at a surface of the earth carrying the drill stringand operable to rotate the drill string; and a control systemoperatively coupled to the reaction valve so as to selectively throttlethe flow of drilling fluid; whereby throttling the flow of drillingfluid creates a differential pressure across the reaction valve and anaxial force that is transferred to the jar so as to urge the mandrel tomove with respect to the sleeve. Embodiments of the assembly forconnection to a drill pipe may generally have: A reaction valve arrangedfor fluid coupling to the drill pipe and to throttle the flow ofdrilling fluid; a jar coupled to the reaction valve, the jar having amandrel that is slidingly received within a sleeve; and a control systemoperatively coupled to the reaction valve so as to selectively throttlethe flow of drilling fluid; whereby throttling the flow of drillingfluid creates a differential pressure across the reaction valve and anaxial force that is transferred to the jar so as to urge the mandrel tomove with respect to the sleeve. Embodiments of the method of drilling awellbore may generally include: Providing a drill string that includes adrill pipe, a jar, and a reaction valve disposed between the drill pipeand the jar, the jar including a mandrel that is slidingly receivedwithin a sleeve; providing a flow of drilling fluid through the drillpipe and the reaction valve; and selectively throttling the flow by thereaction valve so as to create a differential pressure across thereaction valve, the differential pressure creating an axial force thatis transferred to the jar so as to urge the mandrel to move with respectto the sleeve.

Any of the foregoing embodiments may include any one of the followingelements or characteristics, alone or in combination with each other:The reaction valve is disposed above the jar; selectively throttling theflow in a downward direction so as to create a compressive set-downforce that is transferred to the jar; selectively throttling the flow inan upward direction so as to create a tensile force that is transferredto the jar; the force that is transferred to the jar aids in cocking thejar; the force that is transferred to the jar aids in firing the jar;bypassing the flow downstream of the reaction valve from the drillstring to a wellbore annulus; the drill pipe includes an inner pipedisposed within an outer pipe; bypassing the flow in a downwarddirection in the outer pipe to an upward direction in the inner pipe;the reaction valve is coupled to the drill pipe so as to throttle theflow in a downward direction so as to create a compressive set-downforce that is transferred to the jar; the reaction valve is coupled tothe drill pipe so as to throttle the flow in an upward direction so asto create a tensile force that is transferred to the jar; the force thatis transferred to the jar aids in cocking the jar; the force that istransferred to the jar aids in firing the jar; a bypass valve coupled tothe reaction valve and operable to bypass the flow downstream of thereaction valve from the drill string to a wellbore annulus; and a bypassvalve coupled to the reaction valve and operable to bypass the flow in adownward direction in the outer pipe to an upward direction in the innerpipe.

The Abstract of the disclosure is solely for providing the a way bywhich to determine quickly from a cursory reading the nature and gist oftechnical disclosure, and it represents solely one or more embodiments.

While various embodiments have been illustrated in detail, thedisclosure is not limited to the embodiments shown. Modifications andadaptations of the above embodiments may occur to those skilled in theart. Such modifications and adaptations are in the spirit and scope ofthe disclosure.

What is claimed:
 1. A method for drilling a wellbore, comprising:providing a drill string that includes a drill pipe, ajar, and areaction valve disposed between said drill pipe and said jar, said jarincluding a mandrel that is slidingly received within a sleeve; flowingdrilling fluid through said drill pipe and said reaction valve; andselectively throttling said drilling fluid by said reaction valve so asto create a differential pressure across said reaction valve to impartan axial force to said jar so as to urge said mandrel to move withrespect to said sleeve.
 2. The method of claim 1 further comprising:positioning said reaction valve above said jar.
 3. The method of claim 1further comprising: selectively throttling said drilling fluid in adownward direction so as to create a compressive set-down force that istransferred to said jar.
 4. The method of claim 1 further comprising:selectively throttling said drilling fluid in an upward direction so asto create a tensile force that is transferred to said jar.
 5. The methodof claim 1 further comprising: selectively throttling said drillingfluid to facilitate cocking said jar.
 6. The method of claim 1 furthercomprising: selectively throttling said drilling fluid to facilitatefiring said jar.
 7. The method of claim 1 further comprising: bypassingsaid flow downstream of said reaction valve from said drill string to awellbore annulus.
 8. The method of claim 1 further comprising: providingsaid drill pipe with an inner pipe disposed within an outer pipe; andbypassing said flow in a downward direction in said outer pipe to anupward direction in said inner pipe.
 9. A drilling system comprising: adrill string disposed in a wellbore, said drill string including a drillpipe, a jar coupled to said drill pipe and having a mandrel that isslidingly received within a sleeve, and a reaction valve coupled betweensaid drill pipe and said jar, said reaction valve movable between anopen position and a throttled position; a drilling rig carrying saiddrill string and operable to rotate said drill string; and a controlsystem operatively coupled to said reaction valve so as to selectivelyposition said reaction valve; whereby throttling a flow of drillingfluid across said reaction valve creates a differential pressure and anaxial force that is transferred to said jar so as to urge said mandrelto move with respect to said sleeve.
 10. The system of claim 9 furthercomprising: said reaction valve disposed above said jar.
 11. The systemof claim 9 further comprising: said reaction valve coupled to said drillpipe so as to throttle said flow in a downward direction and impart acompressive set-down force to said jar.
 12. The system of claim 9further comprising: said reaction valve coupled to said drill pipe so asto throttle said flow in an upward direction and impart a tensile forceto said jar.
 13. The system of claim 9 wherein: said force that istransferred to said jar aids in cocking said jar.
 14. The system ofclaim 9 wherein: said force that is transferred to said jar aids infiring said jar.
 15. The system of claim 9 further comprising: a bypassvalve coupled to said reaction valve and operable to bypass said flowdownstream of said reaction valve from said drill string to a wellboreannulus.
 16. The system of claim 9 further comprising: said drill pipeincluding an inner pipe disposed within an outer pipe; and a bypassvalve coupled to said reaction valve and operable to bypass said flow ina downward direction in said outer pipe to an upward direction in saidinner pipe.
 17. A jar assembly for connection to a drill pipe, saiddrill pipe forming a conduit for a flow of drilling fluid, the jarassembly comprising: a reaction valve; a jar coupled to said reactionvalve, said jar having a mandrel that is slidingly received within asleeve; and a control system operatively coupled to said reaction valveso as to selectively throttle said flow of drilling fluid across saidreaction valve; whereby throttling said flow of drilling fluid acrosssaid reaction valve creates a differential pressure and an axial forcethat is transferred to said jar so as to urge said mandrel to move withrespect to said sleeve.
 18. The assembly of claim 17 further comprising:said reaction valve disposed above said jar.
 19. The assembly of claim17 further comprising: said reaction valve coupled to said drill pipe soas to throttle said flow in a downward direction and impart acompressive set-down force to said jar.
 20. The assembly of claim 17further comprising: said reaction valve coupled to said drill pipe so asto throttle said flow in an upward direction and impart a tensile forceto said jar.
 21. The assembly of claim 17 wherein said force that istransferred to said jar aids in cocking said jar.
 22. The assembly ofclaim 17 wherein said force that is transferred to said jar aids infiring said jar.
 23. The assembly of claim 17 further comprising: abypass valve coupled to said reaction valve and operable to bypass saidflow downstream of said reaction valve from said drill string to awellbore annulus.
 24. The assembly of claim 17 further comprising: saiddrill pipe including an inner pipe disposed within an outer pipe; and abypass valve coupled to said reaction valve and operable to bypass saidflow in a downward direction in said outer pipe to an upward directionin said inner pipe.